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HOME > Expert Assessments > ENSO Diagnostic Discussion
issued by
March 7, 2002
NOAA Press Release


The evolution towards a warm episode in the tropical Pacific continued during February 2002. Warmer-than-normal sea surface and subsurface temperatures developed throughout the equatorial Pacific during the month (Fig. 1 and Fig. 2, respectively). By late in the month equatorial SST anomalies exceeded +1°C from 165°E to 180 °W (Fig. 1), and in the extreme eastern equatorial Pacific near the South American coast. The warming of surface and subsurface waters along the South American coast was due to the arrival of the oceanic Kelvin wave that has been propagating eastward from the central equatorial Pacific since mid-December. These conditions are often observed in the early stages of El Niņo.

Several of the atmospheric indices indicate that El Niņo/ Southern Oscillation (ENSO) conditions have not developed to the point that guarantees sustained growth of the event. Those indices include the Southern Oscillation Index (Tahiti-Darwin SOI), and both lower-tropospheric and upper-tropospheric wind indices. [Note, these indices are often inconsistent in the early stages of El Niņo, and that they develop El Niņo characteristics as the event evolves.] In contrast, enhanced rainfall has been observed over the tropical west-central Pacific, from Papua New Guinea eastward to the date line (180°W) since the beginning of 2002 (Fig. 3). Enhanced rainfall also developed in late February over the warmer-than-normal waters between the west coast of South America and the Galapagos Islands. These features reflect the warming in the sea surface temperatures, and are possibly the first atmospheric effects of a developing El Niņo.The latest statistical and coupled model predictions show a spread from slightly cooler-than-normal conditions to moderate warm-episode conditions during the remainder of 2002. The coupled models and some statistical techniques that incorporate subsurface oceanic conditions indicate a slow evolution to weak or moderate warm-episode (El Niņo) conditions during the next several months. Other techniques indicate that conditions will remain near normal or even return to slightly colder than normal for the remainder of 2002. The recent evolution in oceanic conditions supports the forecasts of a continued evolution toward El Niņo.

This discussion is a team effort of NOAA and its funded institutions. Updates of SST, 850-hPa wind, OLR and the equatorial subsurface temperature structure are available on the Climate Prediction Center web page at (Weekly Update).  Forecasts for the evolution of El Niņo/La Niņa are updated monthly in CPC's Climate Diagnostics Bulletin Forecast Forum. To receive an e-mail notification when updated ENSO Diagnostic Discussions are released please send your e-mail address to:

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Page Author: Climate Prediction Center Internet Team
Page last modified: March 7, 2002
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